Grounding clip for electrical fixtures

ABSTRACT

Apparatus for providing a reliable grounding path between electrical fixtures and their mounting boxes, particularly where modifications to the conventional nature of the electrical fixtures are unnecessary. A metal clip is disposed as a conductive interface between the mounting yoke of the electrical fixture and the mounting screw utilized to secure the electrical fixture within the mounting box. Low resistance electrical contacts are maintained by disposing spring members on the clip to exert continual contact pressure against both the mounting yoke and the mounting screw. Sharp protrusions extend from the clip to concentrate the contact pressure exerted against the mounting yoke and the mounting screw is engaged by a screw-receiving means on the clip. A spring means is disposed within the screw receiving means to develop the contact pressure and also provides for self-adjustabliity to pitch variations of the mounting screws or to fixed pitch references of the mounting box.

BACKGROUND OF THE INVENTION

The present invention relates to grounding apparatus for electricalfixtures and especially such apparatus which affixes directly to theelectrical fixture without modification thereof. Hitherto, manydifferent devices have been utilized to provide a grounding path betweenan electrical fixture and its mounting box. The most conventionalapproach has been to establish this path with a bonding jumper whichrequires that a wire be attached to both the electrical fixture and themounting box for providing an electrical interface therebetween. Thisapproach is very time consuming and even where sufficient time has beenallotted for the incorporation of the bonding jumper, it isinadvertently disregarded on occasion to thereby result in a hazardouscondition.

Another approach is to establish the grounding path by abutting themounting yoke of the electrical fixture directly against the mountingbox to achieve a metal-to-metal surface contact therebetween. Such ametal-to-metal abutment is not possible in all mounting arrangementsbetween electrical fixtures and mounting boxes and therefore, thisapproach is limited to particular applications. It is also true, thatthe contact resistance resulting at such an abutment between surfaces isvery susceptible to drastic increases from adverse circumstances andtherefore, the reliability of the grounding path established thereby isvery low.

Specially configured metallic clips are utilized in some applications toestablish the grounding path. Disadvantages accompanying the use ofthese clips to achieve a low resistance grounding path between theelectrical fixtures and the mounting box. One such clip is thatdisclosed in U.S. Pat. No. 3,432,793 which is fixedly attached to theelectrical fixture and exerts a spring bias against the mounting screw.Being fixedly attached, this clip can only be utilized if the electricalfixture is modified, therefore, it increases manufacturing costsappreciably and can not be applied directly to conventional electricalfixtures. Another such clip is that disclosed in my U.S. Pat. No.3,663,919 which presents a protruding member to be forcibly wedgedbetween the electrical fixture and the mounting box. Although this clipis highly regarded for its intended purpose, once it is installed, theelectrical fixture becomes more difficult to remove from the mountingbox and thereby may present a problem during maintenance.

SUMMARY OF THE INVENTION

It is therefore a general object of the present invention to provide agrounding path between an electrical fixture and a mounting box with aclip which minimizes and obviates the disadvantages of the prior art.

It is a specific object of the present invention to provide a groundingpath between an electrical fixture and a mounting box with a clip whichmay be applied directly to the electrical fixture without modificationthereof.

It is a more specific object of the present invention to provide agrounding path between an electrical fixture and a mounting box with aclip which in no way inhibits the removal of the electrical fixture fromthe mounting box.

It is another object of the present invention to provide a groundingpath between an electrical fixture and a mounting box with a clip whichexerts a continual contact pressure against both the electrical fixtureand the mounting screw securing the fixture to the box.

It is still another object of the present invention to provide agrounding path between an electrical fixture and a mounting box with aclip which includes a screw-receiving means of self-adjusting pitch.

It is a further object of the present invention to provide a groundingpath between an electrical fixture and a mounting box with a clip havingprotrusions which intensify the contact pressure on the electricalfixture.

These objects are accomplished in one form according to the presentinvention by arranging the members of a U-shaped clip to forcibly gripacross the mounting yoke thickness of conventional electrical fixtures.An aperture is disposed through one member of the clip in alignment witha screw-receiving means through the other member. Protrusions aredisposed on either member to project into the gap separating the membersand serve to facilitate the electrical contact achieved with themounting yoke. Cooperating cantilever springs are incorporated into thescrew receiving means and exert a force against the mounting screwregardless of its pitch variation or the pitch reference established bythe fixed threads within the mounting box.

BRIEF DESCRIPTION OF THE DRAWING

The manner in which these and other objects of the invention areachieved will be best understood by reference to the followingdescription, the appended claims, and the FIGS. of the attached drawingwherein:

FIG. 1 is a partial top view of an electrical fixture mounted into amounting box with the grounding clip of this invention incorporatedtherebetween;

FIG. 2 is a side view thereof with portions of the mounting box cutawayto illustrate the electrical continuity existing between the groundterminal of the electrical fixture and the mounting yoke thereof.

FIG. 3 is an enlarged partial sectional view thereof, takensubstantially along line 3--3 of FIG. 2 to illustrate the self-adjustingpitch feature of the grounding clip and the concentrated contactpressure attained with the protrusions thereof;

FIG. 4 is an enlarged partial sectional view thereof, takensubstantially along line 4--4 of FIG. 1 to illustrate the conductivepath provided between the electrical fixture and the mounting box by thegrounding clip;

FIG. 5 is a top perspective view of the grounding clip;

FIG. 6 is a bottom perspective view thereof; and

FIG. 7 is an enlarged sectional view thereof taken substantially alongthe line 7--7 of FIG. 6 to illustrate the relative disposition of thescrew-receiving means and the protrusions thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawing, and more particularly to FIGS. 1 and 2,there is illustrated an electrical fixture 10 which is secured into amounting box 12 with a grounding clip 14 disposed therebetween inaccordance with this invention. Any suitable electrical fixture 10 couldbe secured into the mounting box 12 but by way of example, a standardduplex receptacle outlet 16 has been chosen for use in this disclosure.To eliminate the safety hazard which would otherwise exist, thegrounding clip 14 provides for the electrical continuity necessary toachieve a grounding path between the outlet 16 and the mounting box 12.

In general configuration, the mounting box 12 is an open endedenclosure, having rectangular sides. The mounting box 12 is fabricatedof conductive metal and is electrically grounded by suitable means, suchas connection to a water pipe (not shown). A mounting flange 18 isprovided on the mounting box 12 and has threaded aperture 20 whichengage with mounting screws 22 in securing the outlet 16 to the mountingbox 12.

The outlet 16 has a generally compatible configuration to that of themounting box 12 and includes a body 24 made of suitable insulatingmaterial, such as moldable plastic. At the front of the body 24,identical but separate grounded receptacles 26 are disposed. Eachreceptacle 26 includes a pair of spaced slots 28 associated withinternal female contacts (not shown) and a semi-circular opening 30associated with an internal female grounding contact (not shown). Thefemale contacts mate with the male contacts of a plug and the femalegrounding contact mates with the male grounding contact on the plug.Screws 32 comprise suitable terminal means for connecting wireconductors to the female contacts and thereby provide for electricallyenergizing the receptacles 26. A metallic mounting yoke 34 extendsacross the rear of the body 24 and is affixed thereto by any suitablemeans, such as folding tabs 36. The mounting yoke 34 is also configuredto extend along both sides of the body 24 and project laterallytherefrom to each side thereof to form mounting ears 38. An elongatedslot 40 is disposed through each mounting ear 38 to permit passage ofthe mounting screw 22 in alignment with the threaded aperture 20 of themounting box 12. A grounding screw 42 comprises suitable terminal meansfor connecting a ground wire to the mounting yoke 34 which in turn iselectrically connected by suitable means (not shown) to the femalegrounding contacts within the receptacles 26.

The grounding clip 14 is made of resilient, conductive material, such asa spring metal strip, in a generally U-shaped configuration whichincludes an upper plate-like member 44 and a lower plate-like member 46,with reference to and as illustrated in FIGS. 5-7. The members 44 and 46are connected to each other at an adjacent end of each, and separated bya gap 48 of less magnitude than the thickness of the mounting ear 38. Anaperture 50 is formed in the upper member 44 and a screw-receiving means52 for engaging with the threads of the mounting screw 22 is disposedthrough the lower member 46, with the longitudinal axes of both theapertures 50 and the screw-receiving means 52 aligned along a commonaxis A-A. Protrusions 54 extend into the gap 48 from the upper member 44and the termination of each member 44 or 46 is configured to divergerelative to the other member 44 or 46 in that an inclined tip 56 isdisposed on the upper member 44 and a locating flange 58 is disposed onthe lower member 46. A spring means 60 of suitable construction, such ascooperating cantilever members 62, is incorporated into the screwreceiving means 52 and a rolled tip 64 is disposed at the end of eachcantilever member 62

In use the grounding clip 14 is applied to the mounting yoke 34 of theoutlet 16 by forcibly directing one of the mounting ears 38 thereof intothe gap 48 separating the upper member 44 from the lower member 46. Aguided entrance 66 is created by the complementary contours of theinclined tip 56 and the locating flange 58 of the members 44 and 46respectively, and serves to facilitate the initial insertion of themounting ear 38 therebetween. The members 44 and 46 are deflected inopposite directions by this insertion which thereby results in contactpressures being exerted against each side of the mounting ear 38.Throughout insertion, the grounding clip 14 is manipulated to align thecommon axis A--A through the slot 40 in the mounting ear 38. Beingdisposed within the gap 48, the protrusions 54 present a relativelysmall contact area against the surface of the mounting ear 38, asillustrated in FIG. 3, and thereby concentrate the contact pressure. Theprotrusions 54 may have any suitable configuration which depends on thecontact pressure to be derived from the deflection attained by themembers 44 and 46. Where the protrusions 54 are configured to derive avery large contact pressure, the surface of the mounting ear 38 isscraped thereby to penetrate any nonconductive substances thereon, andresults in a decreased electrical contact resistance. When assembled,clip 14 is separably mounted on a mounting ear 38.

The outlet 16 is then placed into the mounting box 12 with the commonaxis A--A of the grounding clip 14 aligned along the axis of onethreaded aperture 20 in the mounting flange 18. The mounting screw 22 isthen inserted along the axis of the threaded aperture 20 and turned tosecure the outlet 16 in the mounting box 12. As the mounting screw 22 isturned, the threads thereof engage into both the screw-receiving means52 of the grounding clip 14 and the threaded aperture 20. On thescrew-receiving means 52, the rolled tips 64 are configured and disposedto engage between the threads of the mounting screw 22 and therebyestablish electrical continuity therebetween, as illustrated in FIG. 3.The spring means 60 is disposed on the screw-receiving means 52 forexerting contact pressure against the threads of the mounting screw 22in that the cooperating cantilever members 62 thereof are forced todeflect as the mounting screw 22 is inserted therebetween. This contactpressure is exerted through the rolled tips 64 which are forciblyabutted against the threads of the mounting screw 22 and therefore, adecreased electrical contact resistance is accomplished between thegrounding clip 14 and the mounting screw 22. Due to the deflectablenature of the cantilever members 62, the screw-receiving means 52 isalso self-adjusting the pitch variations between threads on the mountingscrew 22 and to fixed pitch references established by the threadedapertures 20 in the mounting box 12. Although a plurality of cantilevermembers 62 are shown, where desired the spring means 60 could bearranged from a single cantilever member.

The grounding path through which electrical continuity is establishedbetween the electrical fixture 10 and the mounting box 12 is illustratedby the dotted line in FIG. 4. At the mounting ear 38, the protrusions 54are forced to bear against the surface thereof and thereby establish alow resistance interface therebetween. Since the grounding clip 14 ismade of conductive material and the protrusions 54 are an integralportion thereof, electrical continuity exists from the protrusions 54into the upper member 44 and through to the rolled tips 64 on thecantilever members 62 of the lower member 46. The rolled tips 64 areforced to bear against the threads of the mounting screw 22 and therebya low resistance interface is established therebetween. Within thethreaded aperture 20 of the mounting box 12, the engaging threads of themounting screw 22 establish a low resistance interface which is retainedunder a contact pressure by the forces required to secure the outlet 16into the mounting box 12.

It should be readily appreciated by those skilled in this art that theclip embodied by this invention may be applied directly to an electricalfixture without the modification thereof and utilized to accomplish areliable grounding path between the electrical fixture and a mountingbox. Also, the clip exerts continual contact pressure on the electricalinterfaces without inhibiting the removal of the electrical fixture fromthe mounting box and protrusions are disposed on the clip to intensifythe contact pressure exerted against the electrical fixture.Furthermore, the screw-receiving means of the clip is self-adjusting tothe pitch variations between the threads of the mounting screw and tofixed pitch references of the threads within the box.

It should be understood that the present disclosure has been made onlyby way of example and that numerous changes in details of constructionand the combination or arrangement of parts may be resorted to withoutdeparting from the true spirit and the scope of the invention, andtherefore the present disclosure should be construed as illustrativerather than limiting.

What I claim is:
 1. A grounding clip for use with an electrical fixtureof the type having a grounded mounting yoke by which the fixture issecured to a mounting box with mounting screws extending through slotsin the mounting yoke, said grounding clip .[.comprising:.]..Iadd.consisting of .Iaddend.a U-shaped spring having a first member anda second member, said members being substantially flat planar members,said members being separated by a gap of lesser magnitude than thethickness of the mounting yoke, said first member including an aperture,said second member including screw-receiving means aligned with saidaperture for engaging a mounting screw, said screw-receiving meansincluding a pair of cantilever arms, said grounding clip being mountableon the mounting yoke of the electrical fixture with said membersforcibly bearing against the mounting yoke to establish electricalcontinuity therebetween and with said aperture and said screw-receivingmeans aligned with one of the mounting yoke slots to receive a mountingscrew, said cantilever arms being deflectable .Iadd.and having endswhich, in plan, follow straight-line paths at least in the regions wherethey contact the threads of the mounting screw .Iaddend.to slide overand forcibly abut against the threads of the mounting screw inmaintaining electrical continuity therebetween as the mounting screw isaxially engaged into said screw-receiving means.
 2. The grounding clipof claim 1 wherein .Iadd.at a location spaced from said aperture.Iaddend.protrusions extend .[.into said gap.]. from one of said members.Iadd.toward the other to define said gap between the ends of saidprotrusions and the opposing surface of said other member.Iaddend., saidprotrusions being effective to concentrate the contact pressure exertedagainst the mounting yoke and thereby decrease the electrical contactresistance therebetween.
 3. The grounding clip of claim 1 wherein rolledtips are disposed on said screw-receiving means, said rolled tips beingconfigured to engage .[.between.]. threads on the mounting screw andeffectuate the electrical continuity.
 4. The grounding clip of claim 1wherein diverging terminations are disposed on said members, saidterminations being effective to facilitate the disposition of saidgrounding clip on the mounting yoke.
 5. The grounding clip of claim 1wherein protrusions extend .[.into said gap.]. from one of said members.Iadd.toward the other to define said gap between the ends of saidprotrusions and the opposing surface of said other member.Iaddend., saidprotrusions being effective to concentrate the contact pressure exertedagainst the mounting yoke and thereby decrease the electrical contactresistance therebetween; rolled tips are disposed on saidscrew-receiving means, said rolled tips being configured to engage.[.between.]. threads on the mounting screw and effectuate theelectrical coontinuity; diverging terminations are disposed on saidmembers, said terminations being effective to facilitate the dispositionof said grounding clip on the mounting yoke.
 6. In an electrical fixtureof the type adapted to be mounted in an electrically grounded metalmounting box, wherein a metallic mounting yoke supports an insulatedbody and is connected to a grounding contact within said body, saidmounting yoke having at least one mounting ear extending therefrom, saidmounting ear containing a slot to receive a mounting screw therethroughin securing said electrical fixture into the mounting box, theimprovement comprising:a grounding clip detachably affixed to saidmounting ear, said grounding clip .[.being.]. .Iadd.consisting of.Iaddend.a U-shaped spring, said spring having a first member and asecond member, said members being substantially flat planar members,said members being separated by a gap of lesser magnitude than thethickness of said mounting ear, said first member including an aperture,said second member including screw-receiving spring means aligned withsaid aperture for engaging the mounting screw, said grounding clip beingdetachably retained on said mounting ear with said members forciblybearing thereagainst to establish electrical continuity therebetween andwith said aperture and said screw-receiving means aligned with saidslot, said screw-receiving spring means being deflectable .Iadd.andhaving ends which, in plan, follow straight-line paths at least in theregions where they contact the threads of the mounting screw .Iaddend.toslide over and forcibly abut against the threads of the mounting screwin maintaining electrical continuity therebetween as the mounting screwis axially engaged thereinto.
 7. The combination of claim 6 wherein saidscrew-receiving spring means includes a pair of cantilever arms.
 8. Thecombination of claim 7 wherein .Iadd.at a location spaced from saidaperture .Iaddend.protrusions extend .[.into said gap.]. from one ofsaid members .Iadd.toward the other to define said gap between the endsof said protrusions and the opposing surface of said othermember.Iaddend., said protrusions being effective to concentrate thecontact pressure exerted against said mounting yoke and thereby decreasethe electrical contact resistance therebetween.
 9. The combination ofclaim 7 wherein rolled tips are disposed on said cantilever arms, saidrolled tips being configured to engage .[.between.]. threads on themounting screw and effectuate the electrical continuity.
 10. Thecombination of claim 7 wherein diverging terminations are disposed onsaid members, said terminations being effective to facilitate thedisposition of said grounding clip on said mounting yoke.
 11. Thecombination of claim 7 wherein protrusions extend .[.into said gap.].from one of said members .Iadd.toward the other to define said gapbetween the ends of said protrusions and the opposing surface of saidother member.Iaddend., said protrusions being effective to concentratethe contact pressure exerted against said mounting yoke and therebydecrease the electrical contact resistance therebetween; rolled tips aredisposed on said cantilever arms, said rolled tips being configured toengage .[.between.]. threads on the mounting screw and effectuate theelectrical continuity; and diverging terminations are disposed on saidmembers, said terminations being effective to facilitate the dispositionof said grounding clip on said mounting yoke. .Iadd.
 12. A detachablegrounding clip for use with an electrical device of the type employing aconductive mounting yoke for securing the device to a mounting box bymeans of mounting screws having threads which follow a predeterminedhelical path extending through open areas in the mounting yoke, saidgrounding clip consisting of a U-shaped conductive member having firstand second substantially flat planar side members joined together at oneend to form the U-shape, said first side member including an aperturetherethrough, said second side member including an aperturedscrew-receiving means integral therewith and aligned with the aperturein said first side member, said screw-receiving means including aplurality of arms extending toward one another to provide opposed freeedges with an aperture therebetween for engaging threaded portions of amounting screw passing through the apertures in said first and secondmembers, said grounding clip being detachably mountable on the mountingyoke with the apertures therethrough aligned with one of the open areasof the mounting yoke to receive a mounting screw, at least one of saidarms being cantilevered and deflectable to facilitate insertion of themounting screw and engagement and electrical continuity with itsthreads, said arms having ends which follow paths substantiallydifferent from the predetermined path of the threads of the mountingscrew to facilitate sliding over said threads, the spacing between theclosest points of any portions of said opposing side members, beforebeing mounted on the yoke, being less than the thickness of the yoke,whereby when the clip is inserted on the yoke it bears forcibly againstopposite surfaces of the yoke to maintain electrical continuity betweenthe screw-receiving means and the yoke. .Iaddend. .Iadd.
 13. Adetachable grounding clip as defined in claim 12 wherein the opposedfree edges of said arms are substantially parallel to one another..Iaddend..Iadd.
 14. A detachable grounding clip for use with anelectrical device of the type employing a conductive mounting yoke forsecuring the device to a mounting box by means of mounting screwsextending through apertured areas in the mounting yoke, said groundingclip comprising a U-shaped conductive member having first and secondsubstantially flat planar side members joined together at one end toform the U-shape, said first side member including an aperturetherethrough, said second side member having an aperture aligned withthe aperture in said first side member, the aperture through said secondside member having two opposing and substantially parallel edges forreceiving and contacting and sliding over the threads of a mountingscrew passing through the aperture in the first member, at least one ofsaid edges being deflectable by the mounting screw to facilitatereceiving and engaging the threaded portion thereof, said grounding clipbeing detachably mountable on the mounting yoke with the aperturestherethrough aligned with one of the apertures of the mounting yoke toreceive the mounting screw, said parallel edges facilitating insertionof the mounting screw and maintaining electrical continuity with itsthreads, at least one protuberance formed on at least one of said sidemembers and projecting toward the other side member, the spacing betweenthe protuberance and the closest surface of the opposing side member,before being mounted on the yoke, being less than the thickness of theyoke, whereby when the clip is inserted on the yoke electricalcontinuity is established between the clip and the yoke at least by wayof said protuberance. .Iaddend..Iadd.
 15. A detachable grounding clip asdefined in claim 14 wherein the parallel opposite edges defining theaperture through the second side member constitute the only surfaces ofsaid clip which contact the threaded portion of the mounting screw..Iaddend..Iadd.
 16. A detachable grounding clip for use with anelectrical device of the type employing a conductive mounting yoke forsecuring the device to a mounting box with mounting screws extendingthrough open areas in the mounting yoke, said grounding clip comprisinga U-shaped spring having a first member and a second member, the membersbeing substantially flat planar members separated by a gap and at leastone of said members having an outwardly diverging end for facilitatinginitial insertion of the clip on the yoke, said first member includingan aperture, said second member including screw-receiving means integraltherewith and having an aperture aligned with the aperture in said firstmember, said screw-receiving means including a plurality of integralarms extending toward one another to form the aperture in said secondmember, said arms providing substantially parallel, opposed,spaced-apart free ends for engaging and sliding over threaded portionsof a mounting screw, said grounding clip being detachably mountable onthe mounting yoke with the apertures in the first and second membersaligned with one of the openings in the mounting yoke to receive themounting screw, the free ends of said arms being rolled and at least onebeing deflectable to facilitate sliding engagement with the threads ofthe mounting screw and to maintain electrical continuity therebetweenwhen the mounting screw is engaged by said screw-receiving means, aplurality of protuberances projecting from at least one of said memberstoward the other, said protuberances located adjacent the area where atleast one of said members diverges and having inclined surfaces tofacilitate the insertion of the clip on the yoke, the spacing betweenthe innermost ends of said protuberances and the closest surface of theopposing member being less than the thickness of the mounting yokebefore the clip is mounted thereon, whereby when the clip is yieldablyinserted on the yoke electrical continuity is established between thescrew-receiving means and the yoke at least by way of saidprotuberances. .Iaddend. .Iadd.
 17. A detachable grounding clip for usewith an electrical device having a conductive mounting yoke for securingthe device to a conductive mounting box by means of conductive mountingscrews extending through slots in the yoke, said grounding clipconsisting of a U-shaped conductive member having first and secondsubstantially planar side members joined together at one end to form aU-shape, said first side member including an aperture therethrough, saidsecond side member including screw receiving and supporting meansintegral therewith and having an aperture aligned with the aperture insaid first side member, said screw receiving and supporting meansincluding a pair of integral arms having cooperating and opposingsurfaces forming the aperture in said second side member, said opposingsurfaces lying along a non-helical path and being shaped complementaryto one another and dimensioned to receive and make sliding contact witha mounting screw passing through the aperture in the first side member,and being deflectable by said mounting screw to facilitate receiving andslidingly engaging the threaded portion thereof, said grounding clipbeing detachably mountable on the mounting yoke with said aperturestherethrough aligned with one of the slots of the mounting yoke toreceive the mounting screw, said arms maintaining electrical continuitywith said mounting screw, the spacing between the closest points of saidopposing side members, before the clip is mounted on the yoke, beingless than the thickness of the yoke, whereby said side members maintainpressing contact with the opposite surfaces of the yoke. .Iaddend..Iadd.18. A grounding clip as in claim 17 wherein at least one of said sidemembers is flared at the open end of the U-shape to facilitate mountingon the yoke. .Iaddend..Iadd.
 19. A detachable grounding clip for usewith an electrical device having a conductive mounting yoke for securingthe device to a conductive mounting box by means of conductive mountingscrews extending through slots in the yoke, said grounding clipconsisting of a U-shaped conductive member having first and second sidemembers joined together at one end to form a U-shape, said first sidemember including an open area therein, said second side member includingscrew receiving and supporting means integral therewith and having anaperture aligned with the open area in said first side member, saidscrew receiving and supporting means including a pair of substantiallycoplanar arms having cooperating opposing surfaces lying along anon-helical path and forming the aperture in said second side member,the aperture in the second side member being smaller than the open areain the first side member and smaller than the shank of the mountingscrews to be received, at least one of said arms being deflectable bythe mounting screw to receive the screw in sliding engagement andmaintain a pressing contact with said screw, said grounding clip beingdetachably mountable on the mounting yoke with the aperture in thesecond side member aligned with one of the slots of the mounting yoke toreceive the mounting screw, the spacing between the closest points ofsaid opposing side members, before the clip is mounted on the yoke,being less than the thickness of the yoke, whereby said side membersspan the yoke in pressing contact with the opposite surfaces thereof..Iaddend.